Methods and apparatus for roll-coating sheet articles using metering roll of variable profile

Abstract

Methods and apparatus for coating a major surface of a strip article advancing past and in contact with an applicator roll by supplying coating material to the applicator roll for transfer to the strip surface while urging a metering roll against the applicator roll to impart a coating profile to the coating material on the applicator roll before the coating material having that profile is transferred to the strip surface, wherein the metering roll is subjected to a force for bending the axis of the metering roll convexly toward the applicator roll, thereby to compensate for deflection of the metering roll that would otherwise tend to cause nonuniformity of applied coating weight across the width of the strip.

1 . A method of applying a layer of coating material to a major surface of a strip article, comprising
 (a) advancing the strip article along a defined path past a rotating applicator roll urged against said article surface and having an axis transverse to the path, while   (b) supplying coating material to the applicator roll for transporting the coating material thereon and transferring the coating material therefrom to said article surface, and while   (c) urging a rotating metering roll, having an axis generally parallel to the applicator roll axis, against the applicator roll to impart a coating profile to the coating material on the applicator roll before the coating material having said profile is transferred from the applicator roll to said article surface, and while   (d) subjecting the metering roll to a bending force for bending the axis of the metering roll convexly toward the applicator roll.   
     
     
         2 . A method according to  claim 1 , wherein the supplying step comprises supplying coating material to said metering roll such that the supplied coating material is transferred from the metering roll to the applicator roll. 
     
     
         3 . A method according to  claim 1 , wherein the metering roll includes a shaft having opposed end portions respectively projecting beyond opposite ends of the metering roll and respectively engaged by members for transmitting thereto a pressing force directed generally toward the applicator roll rotational axis to press the metering roll against the applicator roll while permitting angular movement of the shaft end portions relative to said members about pivot axes transverse to the metering roll axis, and wherein said bending force is exerted on the shaft end portions outwardly of the members with respect to the metering roll and is directed generally away from the applicator roll rotational axis for bending the metering roll axis convexly toward the applicator roll. 
     
     
         4 . A method according to  claim 3 , wherein the metering roll is hollow, wherein the metering roll shaft extends lengthwise through the metering roll, the metering roll is supported on the shaft for rotation relative thereto by plural spaced bearings, and the bending force to which the metering roll is subjected acts on the shaft and is transmitted by said bearings to the metering roll. 
     
     
         5 . A method according to  claim 3 , wherein the shaft end portions are integral with or fixedly connected to the metering roll, and wherein said members are bearings in which said shaft end portions rotate. 
     
     
         6 . A method according to  claim 1 , including sensing the coating thickness on the strip surface during coating and adjusting the bending force to which the metering roll is subjected to compensate for variations in sensed coating thickness. 
     
     
         7 . A method according to  claim 1 , wherein the applicator roll comprises a rigid core and a resilient outer layer surrounding the core. 
     
     
         8 . A method according to  claim 7 , wherein the strip article is trained over a backup roll that defines, with the applicator roll, a nip through which the strip article passes, the applicator roll being urged against the backup roll. 
     
     
         9 . A method according to  claim 8 , wherein the strip article has opposed major surfaces to be coated, wherein said applicator roll applies coating material to a first major surface of the strip article, and further including applying coating material to the other major surface of the strip article at a location downstream of the aforesaid applicator roll in the defined path, by advancing the strip article in taut condition past the downstream location and urging a second applicator roll against the other major surface of the strip article at the downstream location, the second applicator roll rotating about an axis transverse to the path, while supplying coating material to the second applicator roll for transporting the coating material thereon and transferring the coating material therefrom to the other major surface of the strip article, and while urging a rotating second metering roll, having an axis generally parallel to the second applicator roll axis, against the second applicator roll to impart a coating profile to the coating material on the second applicator roll before the coating material having that profile is transferred from the second applicator roll to the other major surface of the strip article, and while subjecting the second metering roll to a bending force for bending the axis of the second metering roll convexly toward the second applicator roll. 
     
     
         10 . A method according to  claim 9 , wherein the step of supplying coating material to the second applicator roll comprises supplying the coating material to the second metering roll such that the supplied coating material is transferred from the second metering roll to the second applicator roll and thence to said other major surface to be coated. 
     
     
         11 . In apparatus for applying a layer of coating material to a major surface of a strip article advancing along a defined path, in combination:
 (a) an applicator roll assembly including an applicator roll having an axis transverse to the path and a mounting rotatably supporting the applicator roll in facing relation to said article surface while urging the applicator roll against said article surface;   (b) a coating material supply providing coating material to the applicator roll for transport thereon and transfer therefrom to said article surface;   (c) a metering roll having an axis generally parallel to said applicator roll axis and a mounting rotatably supporting the metering roll while urging the metering roll into pressing contact with the applicator roll to impart a coating profile to coating material on the applicator roll before transfer of the coating material having said profile to said article surface; and   (d) roll-bending structure exerting on the metering roll a bending force for bending the metering roll axis convexly toward the applicator roll.   
     
     
         12 . Apparatus as defined in  claim 11 , wherein said coating material supply provides coating material to the metering roll for transfer to the applicator roll and thence to the article surface to be coated. 
     
     
         13 . Apparatus as defined in  claim 11 , wherein the metering roll includes a shaft having end portions respectively projecting beyond opposite ends of the metering roll, wherein the mounting for the metering roll includes members respectively engaging the shaft end portions for transmitting thereto a pressing force directed generally toward the applicator roll rotational axis to press the metering roll against the applicator roll while permitting angular movement of the shaft end portions relative to said members about pivot axes transverse to the metering roll axis, and wherein the roll-bending structure exerts said bending force on the shaft end portions outwardly of the members with respect to the metering roll, as a force directed generally away from the applicator roll rotational axis for bending the metering roll axis convexly toward the applicator roll. 
     
     
         14 . Apparatus as defined in  claim 13 , wherein the metering roll is hollow, the metering roll shaft extends lengthwise through and beyond the metering roll, the bending force exerted by the roll-bending structure acts on the shaft, and the metering roll is supported on the shaft for rotation relative thereto by plural spaced bearings that transmit said bending force to the metering roll. 
     
     
         15 . Apparatus as defined in  claim 13 , wherein the shaft end portions are fixedly connected to the metering roll, and wherein said members are bearings in which said shaft end portions rotate. 
     
     
         16 . Apparatus as defined in  claim 11 , wherein the roll-deflecting structure is mountable, relative to said members, at any of plural locations respectively providing different angular directions of exertion of said bending force relative to the applicator roll. 
     
     
         17 . Apparatus as defined in  claim 11 , wherein the applicator roll comprises a rigid core and a resilient outer layer surrounding the core. 
     
     
         18 . Apparatus as defined in  claim 17 , further including a backup roll that defines, with the applicator roll, a nip through which the strip article passes, the applicator roll being urged against the backup roll. 
     
     
         19 . Apparatus as defined in  claim 18 , wherein the strip article has opposed major surfaces to be coated and said applicator roll applies coating material to a first major surface of the strip article, further including
 (e) a second applicator roll assembly including a second applicator roll and a mounting supporting the second applicator roll for rotation about an axis transverse to the path and in facing relation to the other major surface to be coated at a location in the defined path downstream of the first-mentioned applicator roll, while urging the second applicator roll into pressing contact with said surface, the strip being advanced in taut condition past said downstream location;   (f) a second metering roll having an axis and a mounting supporting the second metering roll for rotation with the second metering roll axis generally parallel to the second applicator roll rotational axis while urging the second metering roll into pressing contact with the second applicator roll;   (g) a second coating material supply providing coating material to the second metering roll for transfer to the second applicator roll and thence to said other major surface; and   (h) second roll-bending structure exerting on the second metering roll a bending force for bending the second metering roll axis convexly toward the second applicator roll.   
     
     
         20 . In a method of applying a layer of coating material to a major surface of a strip article, the steps of:
 (a) advancing the strip article along a defined path past a rotating applicator roll urged against said article surface and having an axis transverse to the path, while   (b) transporting coating material on the applicator roll toward said path for transfer from the applicator roll to said article surface, and while   (c) urging a rotating metering roll, having an axis generally parallel to the applicator roll axis, against the applicator roll to impart a coating profile to the coating material on the applicator roll before the coating material having said profile is transferred from the applicator roll to said article surface, and while   (c) bending the axis of the metering roll convexly toward the applicator roll to compensate for axial deflection of the metering roll away from the applicator roll and thereby to enhance uniformity of coating thickness across the width of the strip article.